Well ill have to say hackamore...but because im a bitless rider...but I own both hackamore and crossover ( crossover being the main preference).
But yea hackamores arnt for every horse. I used a english hackamore on my TB and found him way to sensative to it, but put it on my other horse and he went perfectly in it....so yea. But I still back hackamores up
( minus mechanical ones